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Evolution-change over time
The Origin Of Life
Spontaneous generation vs
biogenesis
A FIRST LIFE HYPOTHESIS
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Conditions one Earth 4.5 billion Years Ago
Amino acids and RNA
Protobionts- Coacervates and Pre-cells
Heterotroph Hypothesis
Cell symbiosis
Miller & Urey’s experiment
• Conditions to simulate a primitive earth• lightning, UV radiation, volcanic activity,
and heating and cooling
• methane, ammonia, carbon dioxide, and
water
• Boiled and condensed
• electric charge
***A mixture of Amino Acids Resulted***
First Life Processes
• 3.5- 4 billion years ago
• 1. Abiotic synthesis of monomers
(amino acids and nucleic acids)
• 2. Joining of monomers into polymers
concentrated by clay, sand, and heat
• 3. aggregation into droplets( protenoids,
liposomes, coacervates- )
• 4. hereditary and metabolic pathways- RNA
and RIBOZYMES
• coacervates, protobionts, precells and the
heterotroph hypothesis
• coacervate- hydrophobic and hydrophilic
portions of large molecules create enclosures
• Proto-cell-precursor of cells ( enclosures with
membrane characteristics
• heterotroph- can NOT make it’s own food and
must consume the molecules from which it
emerged
• Chemoautotroph-use inorganic ( H2S)
compounds to make food
Endosymbiosis
• Eukaryotes resulted from symbiotic
associations between small and large
prokaryotes.
• Ex. mitochondria and chloroplasts have
their own double membrane and DNA
I. Evidence of evolution
Fossils
Comparative Anatomy
Comparative Embryology
Comparative Genetics and
Biochemistry
Systematic
Fossils
mold-impression left by remains in
sediment
imprint- thin carbon film
cast- mold is filled by sediment
petrifaction- replacement by minerals
amber and preserved remains
Mold
Molds
• When an
organism is
buried, it can
decay leaving
an empty space
in the rock
that is the
exact shape of
the organism
Cast-mold is filled in by
sediment
• Mold of an
organism is
created, it often
becomes filled by
minerals in the
surrounding rock,
producing a
replica of the
original organism
Casts
Amber-resin
• Entire, intact
organism
preserved
• Rare, but
valuable
• Most delicate
parts are
preserved
• (DNA)
Petrified fossils
• Hard parts of organisms are penetrated
and replaced by minerals atom-for-atom
• Minerals harden, and an exact stone copy
of the original organism is produced
• Ex. Wood
Imprints
• Fossils form
before
sediments
harden
• Thin objects
like leaves and
feathers falling
into soft
sediments like
mud
• Entire,
intact
organism
preserved
• Rare, but
valuable
• Most
delicate
parts are
preserved
Frozen
Trace fossils
• Markings or
evidence of
animal
activities
• Footprints,
trails, and
burrows
Where are
fossils
found?
Sedimentary
Rocks
Erosion
Law of Superposition
Sedimentary rocks are laid down in horizontal layers with
the younger layers closer to the surface and the older layers
buried deeper. Used to determine the appearance and
disappearance of organisms. Oldest layer? Youngest
Dating Fossils
• Relative Dating – if sediments have
been left undisturbed, layers closer
to the surface should be younger than
deeper layers.
• Absolute Dating – a more precise
measure of age, years, or time period
RELATIVE DATING
• Age determined by relative position of
strata or by fossil similarities
• LAW OF SUPERPOSITION- DEEPER
STRATA ( layers) CONTAIN OLDER
FOSSILS
Relative DATING
• Dates determined by where in strata an
object is found.
• Law of superposition- lower layers are older
and those nearer the surface are more
recent.
Absolute Dating
• Radiometric or Radioactive
Isotope Dating – measuring
the amount of a specific
element found in the
organism that has
radioactively decayed
– Carbon-14 = half-life 5730
years
• Example:
– Carbon –14 Dating
– Half-life – the time (in
years) that passes when half
of the radioactive isotope
decays
RADIOMETRIC DATING
• Use the ratio of radioactive isotope
remaining in a specimen to non-radioactive
parent material.
Half-life- amount of time
needed for 1/2 the radioactive
isotope to decay into a nonradioactive daughter particle
Geologic time scale
• List the four Eras and describe the major
types of life or major geologic event
associated with each:
Geologic Time Scale
• Four Eras
• Most important to know:
– Order of the appearance of organisms
Precambrian Era
• 4.6 billion years – 545
million years ago
• Organisms:
– UNICELLULAR:
Photosynthetic Bacteria and
Primitive Prokaryotes
– 2 billion years into the
Precambrian, first
Eukaryotic organisms
– Towards the end, simple
multi-cellular organisms like
algae, sponges, and jellyfish
Paleozoic Era
• 545 million years – 248 million years ago
• Cambrian period - Life explosion!
– Invertebrates – Worms, echinoderms and primitive
arthropods (trilobites)
– Fish, Plants like ferns on land
– Amphibians
– Reptiles
Mesozoic Era
• 248 million years – 65 million years
• Triassic Period – first mammals (mouse
like) led to dinosaurs
• Jurassic Period – Age of the Dinosaurs
– End of Jurassic – modern birds ancestors
• Cretaceous Period – Dinosaur extinction,
development of flowering plants, oak, fig
and elm trees.
Cenozoic Era
• 65 million –
present
• Mammals
flourish
• Primates
• Modern human
species
approximately
200,000 years
ago
GEOLOGIC
TIME
SCALE
Views of Change over Time
• Gradualismchange in fossil
record is slow
favors Evolution
and Natural
Selection
• Catastophismperiodic natural
disasters have
caused changes
in fossil records
Plate Tectonics
• Geological
explanation for how
the continents
move
• Pangaea – 245
million years ago
• Laurasia and
Gondwana – 135
million years ago
• 7 continents exist –
65 million years ago
Additional Evidence of
Evolution
Anatomical comparisons
Embryological comparisons
Genetic and bimolecular comparisons
Anatomical comparison
• Homologous- similar in origin
• Analogous -similar in function
• Vestigial structures - no apparent
function
Anatomical Analysis
• Homologous
Structure – a
modified
structure that
is seen among
different
groups of
descendants
SIMILAR IN
ORIGIN
Anatomical Analysis
• Analogous Structure – any body
structure that is similar in function
but different in structure SIMILAR
IN FUNCTION
Anatomical Analysis
• Vestigial
Structure –
body structure
that is reduced
in function in a
living organism
but may have
been used in an
ancestor
Anatomical Analysis
• Analogous Structure – any body
structure that is similar in function
but different in structure
Embryological comparisons
Embryological Development
• Similarities
between
vertebrate
embryos
• ex. Gill Slits
and a Tail
Biochemical and Genetic
homology
• Cytochrome and other proteins
are similar
• DNA comparisons
• RNA similarities
• Enzyme comparisons
Genetic Comparisons
• Homology or Similarities within our
DNA
? Evolution as seen by Lamarck1. need 2. Use/disuse 3.
Inheritance of Acquired
Characteristics
• What is wrong with the thinking of
Lamarck concerning the inheritance of
acquired traits?
ADAPTATIONS
• Morphological- change in form (size,
shape, or color)
Physiological- change in body or cell
function
Behavioral- change in the way an
organism interacts with others or it’s
environment
Summary of Natural Selection
• 1. Overpopulation and limited resources
• 2. Genetic variation- genetic drift,mutation,
polyploidy
• 3 Selection pressure- environmental stress
• . 4. The struggle for survival leads to
survival of the most fit genetic variations
which are passed on to succeeding
generations
Overpopulation and selection
pressure
• Bacteria struggle to survive in an
environment with limited
resources.
genetic variation
2. Resistant individuals exist as a
variation but in small numbers
within the bacterial population.
• 2. Repeated use of antibiotics
creates conditions favorable to
selection of resistant individuals
Survival of most fit
• 3. Antibiotic kills non-resistant
members of pop.
Reproduction of most fit
Only resistant survivors in an
unrestricted environment lacking
any competition.
Entire population becomes
resistant
Hardy-WeinbergMicroevolution
• Describes those conditions that can lead to
changes within a population’s genes
GENE POOL- the sum total of all
genes in a breeding population
GENETIC DRIFT- changes in the
frequency of an allele
The gene frequencies of alleles
• For a gene locus where only two genes
occur in a pop. Let p = the frequency of one
allele and q = the frequency of the other.
• Then p + q = 1 ex. ( A + a = 1 )
When gametes combine:
The probability of generating a AA genotype
is p2
The probability of generating a aa genotype
is q2
The prob. of Aa is 2pq
Hardy -Weinberg Principle
States that if the following conditions occur
that the gene pool will not change:
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if matings are random
if there are no mutations
if there are no migrations
if the population remains large
if there is no natural selection
the gene pool will remain constant
These do not all happen in
Nature !!!!!!
The principle is stated as a null hypothesis
Any one of these conditions lead to genetic change?
• If matings are not random not all genes are
shared equally ( Amish, Jews, and other
isolated groups )
• Migrations add to or remove genes
• Mutation- changes gene pool quickly
• Populations are small - inbreeding
• Natural selection favors the most fit
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Evolution of Populations
Hardy-Weinberg theorem describes
microevolution or changes within a
populations gene pool
The equation used to express gene
frequencies within a pop.
P2 +2pq +q2 = 1
The Bottleneck Effect
• Natural disasters reduce the size
of a population. The smaller
population is more subject to
change than the main group.
The Founder Effect
• When a few individuals colonize
a new habitat.
• Galapagos Islands
SPECIES
• Morphological- based on
appearance
• Biological- based on number of
chromosomes ( ability to mate
and produce fertile offspring)
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SPECIATION• the development of a new species from and
existing one
Allopatric speciation
• speciation through isolation of a
population
• geographic isolation
• gene pools become separated
• genetic change ( variation in alleles,
mutation, polyploidy )
• adaptation and natural selection
Sympatric speciation
• Species is formed within a population
• dramatic mutation such as polyploidy
• Ontogeny recapitulates
phylogeny--- our embryonic
development mirrors our
evolutionary past
Industrial Melanism
• Industrial pollution around Manchester
England
• Peppered Moth exists as two variants
Light colored and dark colored living on
light trees covered with lichens.
Selection pressure changes – predation
favors the darker moth variant.
Pesticide resistance
• DDT classic case of natural
selection
• Selection pressure favors DDT
resistant individuals.
• Results in resistant populations.
Three types of selection pressure
• 1. Stabilizing-favors intermediate
phenotype or heterozygote
• 2. Directional - favors one extreme form
or genotype
• 3. Diversifying- favors both extremes or
genotypes
Selection Pressure
• Stabilizing Selection – natural
selection that favors average
individuals of a population
• Average size may be advantageous in
terms of survival and reproduction
• Spiders
Selection Pressure
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Directional selection – one of the
extreme forms of a trait is favored
by natural selection
•
Woodpeckers with the longest
beaks
Selection Pressure
• Diversifying or disruptive selection –
individuals with both extreme forms
of a trait are at a selective advantage
• Limpets – white and dark brown
Mimicry
• Batesian- a harmless species adapt to
resembles a harmful or unpalatable
one- Viceroy/Monarch
• Bee /Robber fly
FLY
WASP
MIMIC
Viceroy Butterfly
MODEL
Monarch Butterfly
Mimicry
• Mullerian – two species that
are harmful or unpalatable
come to resemble each other
over time-Various Species of
Bees
Co-evolution- two species
evolve together
Several symbiotic associations
Parasite-Host
Divergent evolutionbranching out from a
common origin
-adaptive radiation
Convergent evolution-
• two isolated species come to
resemble each other due to
similar environments